/*
 * contrib/hstore/hstore_gist.c
 */
#include "postgres.h"

#include "access/gist.h"
#include "access/stratnum.h"
#include "catalog/pg_type.h"
#include "utils/pg_crc.h"

#include "hstore.h"

/* bigint defines */
#define BITBYTE 8
#define SIGLENINT  4            /* >122 => key will toast, so very slow!!! */
#define SIGLEN    ( sizeof(int)*SIGLENINT )
#define SIGLENBIT (SIGLEN*BITBYTE)

typedef char BITVEC[SIGLEN];
typedef char *BITVECP;

#define SIGPTR(x)  ( (BITVECP) ARR_DATA_PTR(x) )


#define LOOPBYTE \
            for(i=0;i<SIGLEN;i++)

#define LOOPBIT \
            for(i=0;i<SIGLENBIT;i++)

/* beware of multiple evaluation of arguments to these macros! */
#define GETBYTE(x,i) ( *( (BITVECP)(x) + (int)( (i) / BITBYTE ) ) )
#define GETBITBYTE(x,i) ( (*((char*)(x)) >> (i)) & 0x01 )
#define CLRBIT(x,i)   GETBYTE(x,i) &= ~( 0x01 << ( (i) % BITBYTE ) )
#define SETBIT(x,i)   GETBYTE(x,i) |=  ( 0x01 << ( (i) % BITBYTE ) )
#define GETBIT(x,i) ( (GETBYTE(x,i) >> ( (i) % BITBYTE )) & 0x01 )
#define HASHVAL(val) (((unsigned int)(val)) % SIGLENBIT)
#define HASH(sign, val) SETBIT((sign), HASHVAL(val))

typedef struct
{
    int32        vl_len_;        /* varlena header (do not touch directly!) */
    int32        flag;
    char        data[FLEXIBLE_ARRAY_MEMBER];
} GISTTYPE;

#define ALLISTRUE        0x04

#define ISALLTRUE(x)    ( ((GISTTYPE*)x)->flag & ALLISTRUE )

#define GTHDRSIZE        (VARHDRSZ + sizeof(int32))
#define CALCGTSIZE(flag) ( GTHDRSIZE+(((flag) & ALLISTRUE) ? 0 : SIGLEN) )

#define GETSIGN(x)        ( (BITVECP)( (char*)x+GTHDRSIZE ) )

#define SUMBIT(val) (        \
    GETBITBYTE((val),0) + \
    GETBITBYTE((val),1) + \
    GETBITBYTE((val),2) + \
    GETBITBYTE((val),3) + \
    GETBITBYTE((val),4) + \
    GETBITBYTE((val),5) + \
    GETBITBYTE((val),6) + \
    GETBITBYTE((val),7)   \
)

#define GETENTRY(vec,pos) ((GISTTYPE *) DatumGetPointer((vec)->vector[(pos)].key))

#define WISH_F(a,b,c) (double)( -(double)(((a)-(b))*((a)-(b))*((a)-(b)))*(c) )

/* shorthand for calculating CRC-32 of a single chunk of data. */
static pg_crc32
crc32_sz(char *buf, int size)
{
    pg_crc32    crc;

    INIT_TRADITIONAL_CRC32(crc);
    COMP_TRADITIONAL_CRC32(crc, buf, size);
    FIN_TRADITIONAL_CRC32(crc);

    return crc;
}


PG_FUNCTION_INFO_V1(ghstore_in);
PG_FUNCTION_INFO_V1(ghstore_out);


Datum
ghstore_in(PG_FUNCTION_ARGS)
{
    elog(ERROR, "Not implemented");
    PG_RETURN_DATUM(0);
}

Datum
ghstore_out(PG_FUNCTION_ARGS)
{
    elog(ERROR, "Not implemented");
    PG_RETURN_DATUM(0);
}

PG_FUNCTION_INFO_V1(ghstore_consistent);
PG_FUNCTION_INFO_V1(ghstore_compress);
PG_FUNCTION_INFO_V1(ghstore_decompress);
PG_FUNCTION_INFO_V1(ghstore_penalty);
PG_FUNCTION_INFO_V1(ghstore_picksplit);
PG_FUNCTION_INFO_V1(ghstore_union);
PG_FUNCTION_INFO_V1(ghstore_same);

Datum
ghstore_compress(PG_FUNCTION_ARGS)
{
    GISTENTRY  *entry = (GISTENTRY *) PG_GETARG_POINTER(0);
    GISTENTRY  *retval = entry;

    if (entry->leafkey)
    {
        GISTTYPE   *res = (GISTTYPE *) palloc0(CALCGTSIZE(0));
        HStore       *val = DatumGetHStoreP(entry->key);
        HEntry       *hsent = ARRPTR(val);
        char       *ptr = STRPTR(val);
        int            count = HS_COUNT(val);
        int            i;

        SET_VARSIZE(res, CALCGTSIZE(0));

        for (i = 0; i < count; ++i)
        {
            int            h;

            h = crc32_sz((char *) HSTORE_KEY(hsent, ptr, i),
                         HSTORE_KEYLEN(hsent, i));
            HASH(GETSIGN(res), h);
            if (!HSTORE_VALISNULL(hsent, i))
            {
                h = crc32_sz((char *) HSTORE_VAL(hsent, ptr, i),
                             HSTORE_VALLEN(hsent, i));
                HASH(GETSIGN(res), h);
            }
        }

        retval = (GISTENTRY *) palloc(sizeof(GISTENTRY));
        gistentryinit(*retval, PointerGetDatum(res),
                      entry->rel, entry->page,
                      entry->offset,
                      FALSE);
    }
    else if (!ISALLTRUE(DatumGetPointer(entry->key)))
    {
        int32        i;
        GISTTYPE   *res;
        BITVECP        sign = GETSIGN(DatumGetPointer(entry->key));

        LOOPBYTE
        {
            if ((sign[i] & 0xff) != 0xff)
                PG_RETURN_POINTER(retval);
        }

        res = (GISTTYPE *) palloc(CALCGTSIZE(ALLISTRUE));
        SET_VARSIZE(res, CALCGTSIZE(ALLISTRUE));
        res->flag = ALLISTRUE;

        retval = (GISTENTRY *) palloc(sizeof(GISTENTRY));
        gistentryinit(*retval, PointerGetDatum(res),
                      entry->rel, entry->page,
                      entry->offset,
                      FALSE);
    }

    PG_RETURN_POINTER(retval);
}

/*
 * Since type ghstore isn't toastable (and doesn't need to be),
 * this function can be a no-op.
 */
Datum
ghstore_decompress(PG_FUNCTION_ARGS)
{
    PG_RETURN_POINTER(PG_GETARG_POINTER(0));
}

Datum
ghstore_same(PG_FUNCTION_ARGS)
{
    GISTTYPE   *a = (GISTTYPE *) PG_GETARG_POINTER(0);
    GISTTYPE   *b = (GISTTYPE *) PG_GETARG_POINTER(1);
    bool       *result = (bool *) PG_GETARG_POINTER(2);

    if (ISALLTRUE(a) && ISALLTRUE(b))
        *result = true;
    else if (ISALLTRUE(a))
        *result = false;
    else if (ISALLTRUE(b))
        *result = false;
    else
    {
        int32        i;
        BITVECP        sa = GETSIGN(a),
                    sb = GETSIGN(b);

        *result = true;
        LOOPBYTE
        {
            if (sa[i] != sb[i])
            {
                *result = false;
                break;
            }
        }
    }
    PG_RETURN_POINTER(result);
}

static int32
sizebitvec(BITVECP sign)
{
    int32        size = 0,
                i;

    LOOPBYTE
    {
        size += SUMBIT(sign);
        sign = (BITVECP) (((char *) sign) + 1);
    }
    return size;
}

static int
hemdistsign(BITVECP a, BITVECP b)
{
    int            i,
                dist = 0;

    LOOPBIT
    {
        if (GETBIT(a, i) != GETBIT(b, i))
            dist++;
    }
    return dist;
}

static int
hemdist(GISTTYPE *a, GISTTYPE *b)
{
    if (ISALLTRUE(a))
    {
        if (ISALLTRUE(b))
            return 0;
        else
            return SIGLENBIT - sizebitvec(GETSIGN(b));
    }
    else if (ISALLTRUE(b))
        return SIGLENBIT - sizebitvec(GETSIGN(a));

    return hemdistsign(GETSIGN(a), GETSIGN(b));
}

static int32
unionkey(BITVECP sbase, GISTTYPE *add)
{
    int32        i;
    BITVECP        sadd = GETSIGN(add);

    if (ISALLTRUE(add))
        return 1;
    LOOPBYTE
        sbase[i] |= sadd[i];
    return 0;
}

Datum
ghstore_union(PG_FUNCTION_ARGS)
{
    GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
    int32        len = entryvec->n;

    int           *size = (int *) PG_GETARG_POINTER(1);
    BITVEC        base;
    int32        i;
    int32        flag = 0;
    GISTTYPE   *result;

    MemSet((void *) base, 0, sizeof(BITVEC));
    for (i = 0; i < len; i++)
    {
        if (unionkey(base, GETENTRY(entryvec, i)))
        {
            flag = ALLISTRUE;
            break;
        }
    }

    len = CALCGTSIZE(flag);
    result = (GISTTYPE *) palloc(len);
    SET_VARSIZE(result, len);
    result->flag = flag;
    if (!ISALLTRUE(result))
        memcpy((void *) GETSIGN(result), (void *) base, sizeof(BITVEC));
    *size = len;

    PG_RETURN_POINTER(result);
}

Datum
ghstore_penalty(PG_FUNCTION_ARGS)
{
    GISTENTRY  *origentry = (GISTENTRY *) PG_GETARG_POINTER(0); /* always ISSIGNKEY */
    GISTENTRY  *newentry = (GISTENTRY *) PG_GETARG_POINTER(1);
    float       *penalty = (float *) PG_GETARG_POINTER(2);
    GISTTYPE   *origval = (GISTTYPE *) DatumGetPointer(origentry->key);
    GISTTYPE   *newval = (GISTTYPE *) DatumGetPointer(newentry->key);

    *penalty = hemdist(origval, newval);
    PG_RETURN_POINTER(penalty);
}


typedef struct
{
    OffsetNumber pos;
    int32        cost;
} SPLITCOST;

static int
comparecost(const void *a, const void *b)
{
    return ((const SPLITCOST *) a)->cost - ((const SPLITCOST *) b)->cost;
}


Datum
ghstore_picksplit(PG_FUNCTION_ARGS)
{
    GistEntryVector *entryvec = (GistEntryVector *) PG_GETARG_POINTER(0);
    OffsetNumber maxoff = entryvec->n - 2;

    GIST_SPLITVEC *v = (GIST_SPLITVEC *) PG_GETARG_POINTER(1);
    OffsetNumber k,
                j;
    GISTTYPE   *datum_l,
               *datum_r;
    BITVECP        union_l,
                union_r;
    int32        size_alpha,
                size_beta;
    int32        size_waste,
                waste = -1;
    int32        nbytes;
    OffsetNumber seed_1 = 0,
                seed_2 = 0;
    OffsetNumber *left,
               *right;
    BITVECP        ptr;
    int            i;
    SPLITCOST  *costvector;
    GISTTYPE   *_k,
               *_j;

    nbytes = (maxoff + 2) * sizeof(OffsetNumber);
    v->spl_left = (OffsetNumber *) palloc(nbytes);
    v->spl_right = (OffsetNumber *) palloc(nbytes);

    for (k = FirstOffsetNumber; k < maxoff; k = OffsetNumberNext(k))
    {
        _k = GETENTRY(entryvec, k);
        for (j = OffsetNumberNext(k); j <= maxoff; j = OffsetNumberNext(j))
        {
            size_waste = hemdist(_k, GETENTRY(entryvec, j));
            if (size_waste > waste)
            {
                waste = size_waste;
                seed_1 = k;
                seed_2 = j;
            }
        }
    }

    left = v->spl_left;
    v->spl_nleft = 0;
    right = v->spl_right;
    v->spl_nright = 0;

    if (seed_1 == 0 || seed_2 == 0)
    {
        seed_1 = 1;
        seed_2 = 2;
    }

    /* form initial .. */
    if (ISALLTRUE(GETENTRY(entryvec, seed_1)))
    {
        datum_l = (GISTTYPE *) palloc(GTHDRSIZE);
        SET_VARSIZE(datum_l, GTHDRSIZE);
        datum_l->flag = ALLISTRUE;
    }
    else
    {
        datum_l = (GISTTYPE *) palloc(GTHDRSIZE + SIGLEN);
        SET_VARSIZE(datum_l, GTHDRSIZE + SIGLEN);
        datum_l->flag = 0;
        memcpy((void *) GETSIGN(datum_l), (void *) GETSIGN(GETENTRY(entryvec, seed_1)), sizeof(BITVEC))
            ;
    }
    if (ISALLTRUE(GETENTRY(entryvec, seed_2)))
    {
        datum_r = (GISTTYPE *) palloc(GTHDRSIZE);
        SET_VARSIZE(datum_r, GTHDRSIZE);
        datum_r->flag = ALLISTRUE;
    }
    else
    {
        datum_r = (GISTTYPE *) palloc(GTHDRSIZE + SIGLEN);
        SET_VARSIZE(datum_r, GTHDRSIZE + SIGLEN);
        datum_r->flag = 0;
        memcpy((void *) GETSIGN(datum_r), (void *) GETSIGN(GETENTRY(entryvec, seed_2)), sizeof(BITVEC));
    }

    maxoff = OffsetNumberNext(maxoff);
    /* sort before ... */
    costvector = (SPLITCOST *) palloc(sizeof(SPLITCOST) * maxoff);
    for (j = FirstOffsetNumber; j <= maxoff; j = OffsetNumberNext(j))
    {
        costvector[j - 1].pos = j;
        _j = GETENTRY(entryvec, j);
        size_alpha = hemdist(datum_l, _j);
        size_beta = hemdist(datum_r, _j);
        costvector[j - 1].cost = abs(size_alpha - size_beta);
    }
    qsort((void *) costvector, maxoff, sizeof(SPLITCOST), comparecost);

    union_l = GETSIGN(datum_l);
    union_r = GETSIGN(datum_r);

    for (k = 0; k < maxoff; k++)
    {
        j = costvector[k].pos;
        if (j == seed_1)
        {
            *left++ = j;
            v->spl_nleft++;
            continue;
        }
        else if (j == seed_2)
        {
            *right++ = j;
            v->spl_nright++;
            continue;
        }
        _j = GETENTRY(entryvec, j);
        size_alpha = hemdist(datum_l, _j);
        size_beta = hemdist(datum_r, _j);

        if (size_alpha < size_beta + WISH_F(v->spl_nleft, v->spl_nright, 0.0001))
        {
            if (ISALLTRUE(datum_l) || ISALLTRUE(_j))
            {
                if (!ISALLTRUE(datum_l))
                    MemSet((void *) union_l, 0xff, sizeof(BITVEC));
            }
            else
            {
                ptr = GETSIGN(_j);
                LOOPBYTE
                    union_l[i] |= ptr[i];
            }
            *left++ = j;
            v->spl_nleft++;
        }
        else
        {
            if (ISALLTRUE(datum_r) || ISALLTRUE(_j))
            {
                if (!ISALLTRUE(datum_r))
                    MemSet((void *) union_r, 0xff, sizeof(BITVEC));
            }
            else
            {
                ptr = GETSIGN(_j);
                LOOPBYTE
                    union_r[i] |= ptr[i];
            }
            *right++ = j;
            v->spl_nright++;
        }
    }

    *right = *left = FirstOffsetNumber;

    v->spl_ldatum = PointerGetDatum(datum_l);
    v->spl_rdatum = PointerGetDatum(datum_r);

    PG_RETURN_POINTER(v);
}


Datum
ghstore_consistent(PG_FUNCTION_ARGS)
{
    GISTTYPE   *entry = (GISTTYPE *) DatumGetPointer(((GISTENTRY *) PG_GETARG_POINTER(0))->key);
    StrategyNumber strategy = (StrategyNumber) PG_GETARG_UINT16(2);

    /* Oid        subtype = PG_GETARG_OID(3); */
    bool       *recheck = (bool *) PG_GETARG_POINTER(4);
    bool        res = true;
    BITVECP        sign;

    /* All cases served by this function are inexact */
    *recheck = true;

    if (ISALLTRUE(entry))
        PG_RETURN_BOOL(true);

    sign = GETSIGN(entry);

    if (strategy == HStoreContainsStrategyNumber ||
        strategy == HStoreOldContainsStrategyNumber)
    {
        HStore       *query = PG_GETARG_HS(1);
        HEntry       *qe = ARRPTR(query);
        char       *qv = STRPTR(query);
        int            count = HS_COUNT(query);
        int            i;

        for (i = 0; res && i < count; ++i)
        {
            int            crc = crc32_sz((char *) HSTORE_KEY(qe, qv, i),
                                       HSTORE_KEYLEN(qe, i));

            if (GETBIT(sign, HASHVAL(crc)))
            {
                if (!HSTORE_VALISNULL(qe, i))
                {
                    crc = crc32_sz((char *) HSTORE_VAL(qe, qv, i),
                                   HSTORE_VALLEN(qe, i));
                    if (!GETBIT(sign, HASHVAL(crc)))
                        res = false;
                }
            }
            else
                res = false;
        }
    }
    else if (strategy == HStoreExistsStrategyNumber)
    {
        text       *query = PG_GETARG_TEXT_PP(1);
        int            crc = crc32_sz(VARDATA_ANY(query), VARSIZE_ANY_EXHDR(query));

        res = (GETBIT(sign, HASHVAL(crc))) ? true : false;
    }
    else if (strategy == HStoreExistsAllStrategyNumber)
    {
        ArrayType  *query = PG_GETARG_ARRAYTYPE_P(1);
        Datum       *key_datums;
        bool       *key_nulls;
        int            key_count;
        int            i;

        deconstruct_array(query,
                          TEXTOID, -1, false, 'i',
                          &key_datums, &key_nulls, &key_count);

        for (i = 0; res && i < key_count; ++i)
        {
            int            crc;

            if (key_nulls[i])
                continue;
            crc = crc32_sz(VARDATA(key_datums[i]), VARSIZE(key_datums[i]) - VARHDRSZ);
            if (!(GETBIT(sign, HASHVAL(crc))))
                res = FALSE;
        }
    }
    else if (strategy == HStoreExistsAnyStrategyNumber)
    {
        ArrayType  *query = PG_GETARG_ARRAYTYPE_P(1);
        Datum       *key_datums;
        bool       *key_nulls;
        int            key_count;
        int            i;

        deconstruct_array(query,
                          TEXTOID, -1, false, 'i',
                          &key_datums, &key_nulls, &key_count);

        res = FALSE;

        for (i = 0; !res && i < key_count; ++i)
        {
            int            crc;

            if (key_nulls[i])
                continue;
            crc = crc32_sz(VARDATA(key_datums[i]), VARSIZE(key_datums[i]) - VARHDRSZ);
            if (GETBIT(sign, HASHVAL(crc)))
                res = TRUE;
        }
    }
    else
        elog(ERROR, "Unsupported strategy number: %d", strategy);

    PG_RETURN_BOOL(res);
}
